Boiler tube failures are a major cause of forced shutdowns in fossil fuel power plants. As a result of various operational conditions such as heat, pressure, and wear over time, boiler tubes eventually begin to fail by developing circumferential and axial cracks, as well as experience wall thinning (through both erosion and corrosion). When a boiler tube begins to leak, for example, steam escaping through the leak is lost to the boiler environment. Unless the leak is discovered and repaired, the leak may continue to grow until the tube eventually ruptures, thereby forcing the utility operating the boiler to shut it down immediately. These failures prove to be quite expensive for utilities and, as such, early boiler tube leak detection methods are highly desirable.
In boiler systems, tubes may be interconnected by welding material to form a waterwall. As a result of the construction of the tubes to form a waterwall, commercially available scanners are unable to complete a circumferential scan of the tubes. In addition, waterwall tubes are accessible from the hot side of the tubes during a shutdown. The hot side of the tubes is that side that is in direct contact with a flame and the hot gases in the boiler, while the cold side is disposed opposite to the hot side and contacts insulation. Cracking generally occurs at attachment welds at the “cold side” of the tube which is insulated and not easily accessible without insulation removal. Accordingly, it would be desirable to provide an improved scanning device for applications such as boiler tube inspection.